Producing synthetic tanning agents



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Patented 31, 1936 UNITED STATES PATENT OFFICE 2.036.161 PRODUCING SYNTHETIC TANNING AGENTS Hermann Schuette, Mannheim, Germany, assltnor to I. G. Farbenlndustrie Aktiengesellcobalt, Frankl'ort-on-the-Main, Ge

rmany No Drawing. Application July 21, 1934, Serial No. 737,260. In Germany August 8, 1933 Claims.

d, ior example irom iio to 160 C. As initial materials tor the process according to this invention there may be mentioned, for example, ial-dihydroxydiphenylsulphone, a.a'-dihydroxyt5'-dimethyldiphenylsulphone, 2.2'-dihydroxydiphenylsulphone and also sulphones containina substituents, such as, for example, halogen atoms. The salts or sulphurous acid, tor example, sodium, potassium or ammonium sulphite, and iormaldehyde or trioxymethylene may be added to the said dlphenylsulphones in aqueous solution. it is preferable to worlr at temperatures above lilll l3. and while employing pressure, lor trample, by operating in a closed vessel. The amounts or iormaldehyde and sulphurous acid salts to be employed are advantageously so se-- lected that one or two --JUH2-SO3H groups enter into the molecule of the sulphone. any intermediate amounts may also be employed. Ii only the amount of formaldehyde be increased, a con-l densation oi the sulphones with each other talres place. 4

The condensation products prepared accord me to this invention yield, alter tanning, a leather which is distinguished by its iastness to light and winch entirely fulfills the requirements of the modern leather industry. They are especially suitable tor the manufacture of leather last to light tor uppers, portfolios and furniture, and. ior tanning reptile leathers in which it is desired to retain especially well the fineness of the deslun and the shade or colour. The said tanning agents lreuuently have a very coed iullina action. They may be advantageously employed tocether with other natural or vegetable tannins agents, such as, for example, sumach or pail nut extract, or toeether with other synthetic tanning agents, for instance, those described in the copendinu application Ser. No. 727,913 or in Patent No. 1,336,759 and in Patent No. 1,237,405; i'urthermore they influence very favorably the colour of the leather obtained by mineral (chrome) tanning.

The tanning agents obtainable according to the present invention, when in the form oi a. l per cent aqueous solution, yield, by the addition of 5 a dilute aqueous solution of iron chloride, 9. reddish violet colouration which soon becomes turbid by the deposition of a reddish violet precipitate.

The following examples will further illustrate the nature of this invention, but the invention id is not restricted to these examples. the parts are by weight.

Example 1 125 parts oi id'-dlhydroxydiphenylsulphone 1a are introduced into a solution oil 126 parts oi calcined sodium sulphite and its parts oil so per cent aqueous formaldehyde in soo parts of water, the whole being heated for so hours at from 155 to 160 (2. in a closed vessel. A yellowisl'i-brown, clear solution is obtained; it is rendered acid to congo by means of a little, from to per cent aqueous sulphuric acid, boiled for a short time and filtered it necessary. The solution is then evaporated on a waterbath until it has a syrupy consistency or at room temperature in vacuo to dryness until a pale yellowish mass is obtained. ll. tannins agent is thus obtained which is especially suitable tor tanning reptile leather.

it'll trample 2 m 125 parts of id"-dihydroxydiphenylsulphone are introduced into a solution oil parts oi calcined sodium sulphite, and parts oil 35 35 per cent aqueous formaldehyde in sec parts oi water; the whole is then heated for d hours at C. in an autoclave. An aqueous solution is obtained which is diluted with about the same weight of water and then rendered acid to eoneo as with dilute aqueous sulphuric acid of from about 20 to 25 per cent strength. The solution is then boiled for a short time, iiltered it necessary and evaporated on a waterbath to cive a viscous mass or in vacuo to dryness to give a dry, pale yellowish mass.

By the addition or concentrated hydrochloric acid to the aqueous solution, the reaction product may also be precipitated in the form of a colour less mass which may be separated alter sedimentation and then freed from any hydrochloric acid and water still present by allowing it to stand over caustic soda at room temperature in VECUQ. 5%

tcr in a'cloced vessel to a temperature between 140 and 160 C.

10. Tanning agents originating from the reaction of a dihydrondiphenylsulphone, a water 'soluble salt of sulphurous acid and a formaldehyde substance.

11. Tanning agents originating from the reactionof. a dihydroxydiphenylsulphone, a watersoluble salt of sulphurous acid and formaldehyde.

12. Tanning agents originating from the reaction of 4.4'-dihydroxydiphenylsulphone, a wateraoluble salt of sulphurous acid and formaldehyde.

13. Tanning agents originating from the reaction of 1 molecular proportion of 4.4'-dihydroxydiphenylsulphone, 1 molecular proportion of a water-soluble salt of sulphurous acid and 1.2 molecular proportions of formaldehyde.

14. Tanning agents originating from the reaction of 1 molecular proportion of 4.4'-dihydroxydiphenylsulphone, 1.2 molecular proportions of a water-soluble salt of sulphurous acid and 2 molecular proportions of formaldehyde.

15. Tanning agents originating from the reaction of 1 molecular proportion of 4.4'-dihydroxydiphenylsulphone, 2 molecular proportions of a water-,aoluble salt of sulphurous acid and 2 molecular proportions of formaldehyde.

HERMANN SCHUEI'I'E. 

